It has heretofore been put into practice to bury copyright management information in contents data such as digital audio data. For example, in case of digital audio data, it has been proposed to bury so-called “Buried-data” in the audio data for executing the copyright management.
Details about the buried-data will be explained later when describing the embodiment. In short, the additional information other than the contents data is arranged by making use of several bits, each of which belongs to each sector and is the least significant bit of digital data whose one sample includes, e.g. sixteen bits. To make output sound when audio data including the buried-data are reproduced remain the same as output sound when the audio data not yet including the buried-data are reproduced, some modifications are usually made on audio data in sections other than those including the buried data. In addition, it is designed that the buried-data is not arranged in sections where audio data are mute data.
By burying the buried-data having the copyright management information in the contents data such as audio data, satisfactory management of copyright of those contents can be performed using the buried-data. Because the buried-data buried in the contents data will remain as it is, unless compression processing or the like is performed on the contents data. Thus, as compared with a case where copyright management information is added as additional information like subcode which is different from audio data itself, it is difficult to alter or remove the copyright management information, so that the management of copyright can be carried out effectively.
Incidentally, when the management of copyright on audio data, etc. is carried out, there are cases where the modifications of copyright information are required depending on use conditions of its contents. However, when the buried-data is used, hardware within apparatus must bear a heavy burden to execute processings for the modification. This poses a problem.
Specifically, the copyright information in contents data such as audio data may include information on limiting the number of times of copying. For example, there may be a case where copying of contents is permitted only once. On such occasion, when reproducing original data and then recording the reproduced data in some medium, it is necessary to revise old buried-data, which is contained in the reproduced original data and indicates that copying is allowed once, to new buried-data indicating that no copying is allowed, before recording it in the medium. To execute such revision processing, however, it is necessary to extract the buried-data from the contents data, revise the buried-data that is extracted, and bury the buried-data that is revised in the contents data. Because the buried-data is primarily recorded for preventing a wrong use, it is designed to make the processing difficult. When some circuit for the processing is provided in a data recording apparatus or the like, the structure of apparatus goes complicated accordingly. This poses the aforesaid problem.
Additionally, although the problem has been described, which is posed when the buried-data is buried in audio data for use, the same problem will also be raised when processing additional information which is buried in other various contents data.